Co(Ⅲ)/Zn(Ⅱ)-catalyzed dearomatization of indoles and coupling with carbenes from ene-yne ketones via intramolecular cyclopropanation

A straightforward and efficient protocol for dearomatizing indoles is described.The reaction,catalyzed by an inexpensive Co(III)/Zn(II)catalyst,starts from easily accessible N‐pyrimidinyl indoles and ene‐yne ketones.Mild reaction conditions,high diastereoselectivity,a broad substrate scope,effective functional group tolerance,and reasonable to remarkable yields were observed.

Design Strategy of Infrared 4-Hydroxybenzylidene-imidazolinone-Type Chromophores based on Intramolecular Charge Transfer:a Theoretical Perspective

Partial genetically encoded 4-hy-droxybenzylidene-imidazolinone(HBI)-type chromophores are new promising fluorescent probes,which are suitable for imaging and detection of living cells.How-ever,the lack of infrared chro-mophores hinders the develop-ment seriously.Here more than 30 HBI-type chromophores with reg-ular structure modifications were employed and typical spectral redshift change laws and mechanisms were investigated by quantum methods.Results show that both one-photon spectrum(OPS,absorption/emission)and two-photon absorption(TPA)can achieve large redshift via either extending conjugated lengths of frag-3 or enlarging conjugated areas of frag-1 of HBI skeleton.Spectral redshifts of all chromophores are highly related to intramolecular charge transfer(ICT),but neutral ones are closely related to the total ICT or electron-accept-ing-numbers of frag-3,and the high correlative factor of anions is the aromaticity of frag-2 bridge.The frag-2 bridge with high aromaticity can open a reverse charge transfer channel in anion relative to neutral,obtaining significant redshift.Based on analysis,a new 6-hydroxyl-naphthalene-imidazolinone(HNI)series,which have larger conjugated area in frag-1,are pre-dicted.The OPS and TPA of anionic HNI ones acquire about 76−96 nm and 119−146 nm red-shift relative to traditional HBI series respectively as a whole.The longest emission of anionic HNI-4 realizes more 244 nm redshift relative to HBI-1.Our work clarifies worthy spectral reg-ularities and redshift mechanisms of HBI-type chromophores and provides valuable design strategy for infrared chromophores synthesis in experiment.

Copper-catalyzed amination of phenylboronic acids with benzofurazan 1-oxides

CuCl/Phen can catalyze the C–N coupling between arylboronic acid and benzofurazan1‐oxide.This reaction occurred under mild and redox‐neutral conditions with benzofurazan1‐oxide as an aminating reagent via ring scission,leading to a bifunctionalized aminonitrobenzene.

Divergent Synthesis of Organofluorinated Molecules from Titanium Mediated Deoxygenation of Free Alcohols

Comprehensive Summary Alcohols as among the most widely occurring organic compounds known,deoxygenative transformations of free alcohols as partners in radical addition reactions remain formidable challenges with great opportunities to achieve new and useful transformations.Herein,we report a protocol via C—O bond cleavage and C—C bond-forming reaction of trifluoromethyl alkenes with free alcohols assisted by titanium reagents via a deoxygenative radical strategy,enabling the divergent synthesis for functional-group-rich organofluorinated compounds in high efficiencies.In this transformation,tertiary alcohols by Ti-catalysis could be converted to trifluoromethyl alkanes without defluorination in acidic conditions,while benzyl alcohols are employed by Ti-mediated activation to supply the gem-difluoroalkenes with defluorination in the presence of a base.This protocol is applicable for a broad range of trifluoromethyl alkenes with good functional group tolerance and a variety of tertiary alcohols and benzyl alcohols(including primary。

Enantioselective Conjugate Addition-Protonation of 5H-Oxazol-4-ones and 5-Methylene 1,3-Oxazolidine-2,4-diones: 2,2'-Biphenol-lnduced Diastereoselectivity Switch

A synthetic strategy for catalytic asymmetric conjugate addition-protonation and diastereoselective switch between 5H-oxazol-4-ones and 5-methylene 1,3-oxazolidine-2,4-diones was established.An array of chiral conjugate addition-protonation products bearing 1,3-O-heterotertiary-O-heteroquarternary nonadjacent stereocenters were obtained in excellent yields,moderate to good diastereoselectivities,and excellent enantioselectivities (up to 97% yield,11:1 dr,and 98% ee).Induction by 2,2'-biphenol could effectively promote the production of the corresponding diastereoisomers via cycloaddition intermedia.

Recent Progress in Endoplasmic Reticulum-Targetable Small-Molecule Probes for Fluorescence Sensing and Phototherapy

The endoplasmic reticulum(ER)is the most widespread organelle within eukaryotic cells,performing various essential functions such as protein synthesis,post-translational modifications,and lipid metabolism.Abnormal fluctuations of biologically active species and microenvironments in the ER can disrupt homeostasis and eventually lead to ER stress,which is closely linked to the occurrence and progression of many human diseases.Therefore,the ER has been regarded as an important analytical object as well as a promising therapeutic target in both bio sensing and biomedicine.Recently,there has been a growing interest in developing photon-excited molecular tools to uncover the physio pathological roles of ER and treat ERrelated disorders.This review presents a comprehensive summary of recent advances in ER-targeted small-molecule probes and their applications for fluorescent sensing and phototherapy,mainly focusing on targeting strategies and probe design principles.Last,we discuss the challenges involved with ER-targeted probes and highlight potential prospects in this field.

Merging a Negatively Curved Nanographene and a Carbon Nanoring

Two molecular nanocarbons result from merging a negatively curved nanographene and a carbon nanoring in two constitutional isomers of D2 and C2v symmetry,respectively.They were synthesized by attachment o f C-shaped paraphenylene precurso rsto 2,11,18,27-tetrabromooctabenzo[8]circulene and the subsequent intramolecular Yamamoto coupling and reductive aromatization reactions.The flexible nature of octabenzo[8]circulene enabled two different ways of connection in the Yamamoto coupling reactions,leading to the two constitutional isomers.The D2 isomer is shaped like a figure eight,as revealed by X-ray crystallography,and is resolved into two enantiomers by chiral HPLC.The synthesis of the C2v isomer is regarded as a further step toward precision synthesis of carbon schwarzites through a bottom-up approach.

Single Particle Colorimetric Acid Phosphatase Activity Assay with CeO_(2)-modified Gold Nanoparticles

Acid phosphatase(ACP)is a ubiquitous phosphatase in living organisms.The abnormal variation of ACP is related to various diseases.Herein,we propose a colorimetric method based on CeO_(2)-modified gold core shell nanoparticles(Au@CeO_(2)NPs)to analyze ACP activity with high sensitivity and specificity.In this design,2-phospho-L-ascorbic acid trisodium salt(AAP)is dephosphorylated by ACP and produces reductive ascorbic acid(AA),which makes the CeO_(2)shell decomposition.A remarkable blue shift of localized surface plasmon resonance peak(LSPR,from yellow to green)along with the scattering intensity ratio changes from individual Au@CeO_(2)NPs are observed.ACP activity can be quantified by calculating the ratio changes of individual Au@CeO_(2)NPs.This assay reveals limit of detection(LOD)of 0.044 mU/mL and the linear range of 0.05–5.0 mU/mL,which are much lower than most of spectroscopic measurements in bulk solution.Furthermore,the recovery measurements in real samples are satisfactory and the capacity for practical application is demonstrated.As a consequence,Au@CeO_(2)NPs used in this assay will find new applications for the ultrasensitive detection of enzyme activity.

Azvudine(FNC):a promising clinical candidate for COVID-19 treatment

A very recent work published in Advanced Science by our group reveals that 2′-deoxy-2′-β-fluoro-4′-azidocytidine(Azvudine,FNC),a clinical candidate originally developed for HIV treatment,has entered clinical trial in China for evaluating its efficacy and safety(ChiCTR2000029853),showing promise for treating novel coronavirus disease 2019(COVID-19).1 This work suggests that nucleoside-based antivirus agents could be repurposed for COVID-19 treatment.

Azvudine is a thymus-homing anti-SARS-CoV-2 drug effective in treating COVID-19 patients

Azvudine(FNC)is a nucleoside analog that inhibits HIV-1 RNA-dependent RNA polymerase(RdRp).Recently,we discovered FNC an agent against SARS-CoV-2,and have taken it into Phase III trial for COVID-19 patients.FNC monophosphate analog inhibited SARS-CoV-2 and HCoV-OC43 coronavirus with an EC_(50) between 1.2 and 4.3 μM,depending on viruses or cells,and selective index(SI)in 15-83 range.Oral administration of FNC in rats revealed a substantial thymus-homing feature,with FNC triphosphate(the active form)concentrated in the thymus and peripheral blood mononuclear cells(PBMC).Treating SARS-CoV-2 infected rhesus macaques with FNC(0.07 mg/kg, qd,orally)reduced viral load,recuperated the thymus,improved lymphocyte profiles,alleviated in flammation and orga n damage,and lessened grou nd・glass opacities in chest X-ray.Sin gle-cell seque ncing suggested the promotion of thymus function by FNC.A randomized,single-arm clinical trial of FNC on compassionate use(n=31)showed that oral FNC(5 mg,qd)cured all COVID-19 patients,with 100%viral ribonucleic acid negative conversion in 3.29±2.22 days(range:1-9 days)and 100%hospital discharge rate in 9.00±4.93 days(range:2-25 days).The side-effect of FNC is minor and transient dizziness and nausea in 16.12%(5/31)patients.Thus,FNC might cure COVID-19 through its anti-SARS-CoV-2 activity concentrated in the thymus,followed by promoted immunity.

Visible Light-Driven Cooperative DPZ and Chiral Hydrogen-Bonding Catalysis

What is the most favorite and original chemistry developed in your research group?The visible light photosensitizer DPZ.How did you get into this specific field?Could you please share some experiences with our readers?Since I began my postdoctoral work at NUS,chiral hydrogen-bonding catalysis,an important branch of asymmetric organocatalysis,has become the general area of focus of my research.To broaden the applications of this strategy,I proposed to exploit photocatalysis to generate highly reactive radical intermediates,thus overcoming the current limitations in both reaction and substrate types stemming from the low energy of hydrogen-bonding interactions.The development of highly efficient organophotocatalysts and explorations of transition metal-free cooperative photocatalysis and chiral hydrogen-bonding catalysis have therefore been my research focus since 2013.My students and I strive to follow the saying"stick to the research direction,thoroughly understand the scientific challenges,and face those challenges with optimism and determination".

Synthesis of polycyclic spiro-fused indolines via IBX-mediated cascade cyclization

We report a 2-iodoxybenzoic acid(IBX)-mediated intarmolecular oxidative spiro-fused tandem cyclization reaction of tryptophan analogs bearing an N-arylamides side-chain to rapidly afford polycyclic spiroindolines featuring multiple stereocenters including a quaternary stereocenters under mild reaction conditions.Among them,a novelty azaphosphol idine-containing spiroindoline compound is synthesized for the first time.It may open the door to azaphos pholidine-containing spiroindoline compound of potential interest in synthetic and medicinal chemistry.A plausible mechanism is proposed.

Selenium-catalyzed Oxidative Carbonylation of Benzylamines to 1,3-Dibenzylureas

A facile, efficient and cost-effective approach to 1,3-dibenzylurea was reported. With cheap and recycla- ble nonmetal selenium as catalyst, carbon monoxide instead of phosgene derivatives as earbonylation agent and oxygen as oxidant, the selenittm-catalyzed oxidative carbonylation reaction of benzylamines can proceed efficiently in one-pot manner in the presence of triethylamine to afford the desired 1,3-dibenzylttreas mostly in moderate to excellent yields. Selenium catalyst can be easily recovered due to its vhase-transfer catalvtic function and recycled

Selenium-catalyzed oxidative carbonylation of 1,2,3-thiadiazol-5-amine with amines to 1,2,3-thiadiazol-5-ylureas

A facile one-pot, economical approach to 1,2,3-thiadiazol-5-ylureas was developed via seleniumcatalyzed oxidative carbonylation of 1,2,3-thiadiazol-5-amine with a series of amines in one-pot manner in the presence of CO and O_2. This approach is featured with cheap and easily available raw materials,cheap and reusable catalyst selenium, one-pot procedure, high atomic economy, simple operations and no emission of corrosive wastes.

Dimethyl sulfoxide-aided copper(0)-catalyzed intramolecular decarbonylative rearrangement of N-aryl isatins leading to acridones

Described here is the first example of Cu(0)-catalyzed intramolecular decarbonylative rearrangements of readily available N-aryl isatins assisted by solvent dimethyl sulfoxide(DMSO)under air atmosphere and additive-free conditions leading to various biologically important acridones in good to excellent yields.This novel transformation is proposed to go through a sequential DMSO-aided Cu insertion into the amide C-N bond,CO extrusion,Cu migration,reductive elimination and DMSO-aided proton migration processes,involving multiple types of bond cleavage and formation in a single chemical step.

2,11-Dimethoxyldipyridopurinone as an efficientreducing visible-light photocatalyst for organic transformations

We report for the first time 2,11-dimethoxyldipyridopurinone (DP4) as a potent reducing visible-lightphotocatalyst toward three prototypic organic transformations: redox-neutral intramolecular aryltrifluoromethylations of acrylamides and the direct C–H arylation of heteroarenes with aryl diazonium salts, netoxidative hydroxylations of arylboronic acids using molecular oxygen as a green oxidant, and the netreductive dehalogenation/deuteration of α-bromocarbonyl compounds. This work reveals a bright futurefor dipyridopurinone derivatives as a new class of metal-free visible-light photocatalysts for a wide rangeof organic transformations.